Used in an index, unless the column is a varchar, nvarchar, or varbinary data type, the data type is not changed, and the new size is equal to or larger than the old size.

Used in statistics generated by the CREATE STATISTICS statement. First remove the statistics using the DROP STATISTICS statement. Statistics automatically generated by the query optimizer are automatically dropped by ALTER COLUMN.

Used in a PRIMARY KEY or [FOREIGN KEY] REFERENCES constraint.

Used in a CHECK or UNIQUE constraint, except that altering the length of a variable-length column used in a CHECK or UNIQUE constraint is allowed.

Associated with a default, except that changing the length, precision, or scale of a column is allowed if the data type is not changed.